Killer Octave

[Tom Servinsky]

Ron,
The reason for my inquiry was a Knabe grand we had to deal with, which
should have had a new board installed but the customer wasn't about to spend
the extra money...you get the picture.
We reluctantly ended up taking the job and ended having a terrible time with
a distortion/harmonic in the 6th octave. The board appeared to be well-glued
around the perimeter and all ribs appeared to well in tact.  However we were
still getting a noticeable buzz/harmonic on D#6 and E6 on hard blows, but no
where else.  By putting some pressure on that part of the board
 underneath) it was apparent it was coming from the corresponding
rib/soundboard area. There was crown and bearing both present, ribs
appearing in tact, but with this annoying distortion.  I couldn't get a
wedge to help matters due to no brace in the area. I ended up, as a last
ditch effort, configuring a connecting brace where I could at least get a
wedge secured and the distortion was eliminated. However, as one knows,
wedging the soundboard to the brace also has gross limiting factors as it
stifles the ability of the soundboard to do it's thing. Then I started
horsing around with the idea of a spring to (at least) apply upwards
pressure to help alleviate the problem.
Of course I was treating the symptom and not the problem.  The piano needed
a new board, the customer wasn't the position to deal with the extra
expense, and I had my ego trying to do anything and everything possible to
make matters better.
So I guess the bigger picture is soundboards can have an inherent weak spot
due to (either) weakness in wood strength, design, or just age, even though
the bearing and crown under pressure appear to be in good standing.
Could the idea of the spring, as taboo as it sounds, help alleviate problems
such as these?
Tom Servinsky,RPT
Tom Servinsky,RPT
----- Original Message -----
From: "Ron Nossaman" <RNossaman@KSCABLE.com>
To: <pianotech@ptg.org>
Sent: Saturday, September 08, 2001 3:51 PM
Subject: Re: Killer Octave


> >Ron,
> >I came late in the discussion about soundboard springs when it was being
> >talked about last. I've caught tail-ends of this discussion in the past
but
> >never got the whole gist of the spring.   Could you elaborate the spring
> >concept and describe physically how and where these would be installed?
> >Tom Servinsky,RPT
>
> Tom,
> This was something Del said he experimented with briefly some years back.
A
> few automotive valve springs are mounted on supports between beams,
> positioned underneath the soundboard along the bridge line, boosting the
> inadequately stiff soundboard up to try to get some tone back. He reported
> some improvement, but apparently nearly got lynched for soundboard heresy
> before he got too far into the research.
>
> Ron N